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Physiological characterization of a plastidic signal required for nitrate-induced appearance of nitrate and nitrite reductases (1988)

Oelmüller, R. ; Schuster, C. ; Mohr, H.

Springer

Planta 174 (1988), S. 75-83

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ISSN: 1432-2048

Keywords: Nitrate reductase ; Nitrite reductase ; Phytochrome ; Plastidic signal ; Sinapis

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We compared the response of NO 3 - -induced nitrate-reductase (NR) and nitrite-reductase (NIR) levels in virtually carotenoid-free far-red-light-grown mustard (Sinapis alba L.) cotyledons following a photooxidative treatment of the plastids. The cytosolic localization of NR and the plastidic localization of NIR were confirmed with this approach. Emphasis was on a plastidic factor previously postulated to be involved obligatorily in the transcriptional control of nuclear genes coding for proteins destined for the chloroplast. Photooxidative damage of the plastid would be to destroy the ability of the organelle to send off this signal. Dependency of NIR and NR induction by NO 3 - on the plastidic factor is described in detail, and it is concluded that requirement for the plastidic factor is relatively high in the case of NR while factor requirement to allow induction is low in the case of NIR. The data indicate that in the case of NIR the photooxidative damage done to the plastid also affects accumulation of the enzyme directly. Since this effect is absent in the case of cytosolic NR, induction of NR is a particularly suitable system for further molecular studies of the plastidic factor and its mode of action.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00394876

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Recovery of plastids from photooxidative damage: Significance of a plastidic factor (1988)

Schuster, C. ; Oelmüller, R. ; Bergfeld, R. ; [et al.]

Springer

Planta 174 (1988), S. 289-297

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ISSN: 1432-2048

Keywords: Chloroplast (photooxidation, proteins) ; mRNA (chloroplast proteins) ; Nitrate reductase ; Photooxidation (chloroplast) ; Sinapis (plastid photooxidation)

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract It was inferred from previous findings that a plastid-derived factor (plastidic factor) is involved in the transcriptional control of nuclear genes coding for proteins destined for the chloroplast. Photooxidative damage to the plastid destroys the ability of the organelle to give off this factor. Cytosolic enzyme levels are not impaired if plastids are damaged, and morphogenesis of seedlings is normal. The only exception found so far is nitrate reductase, a cytosolic enzyme, which is regulated by the cellas if it were a plastidic protein. In the present study we have shown that the plastids in the mesophyll of mustard (Sinapis alba L.) cotyledons, damaged by 3 h photooxidation in red light (6.8 W·m-2) and then returned to darkness or to continuous, non-photooxidative far-red light (cFR), recover from photooxidative damage. The rate of recovery is stimulated by phytochrome (operationally, cFR). Since the cytosolic enzyme nitrate reductase is affected by the different treatments in principally the same way as the levels of plastidic enzymes, we conclude that it is recovery of the plastids' ability to give off the plastidic factor rather than structural recovery which leads to recovery of gene expression and protein (and chlorophyll) re-accumulation. The extent of recovery varied according to the enzyme and this variation could be explained by different plastidic-factor requirements for gene expression. This explanation was confirmed by measurements of translatable mRNAs. It was found that LHCP-gene expression (light-harvesting chlorophyll a/b-binding protein of photosystem II) is far more sensitive to photooxidative damage of the plastids than SSU-gene expression (small subunit of ribulose-1.5-bisphosphate carboxylase). Correspondingly, recovery is expressed to a much greater extent in the latter than in the former case.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00959512

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3

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Effect of nitrate, ammonium, light and a plastidic factor on the appearance of multiple forms of nitrate reductase in mustard (Sinapis alba L.) cotyledons (1989)

Schuster, C. ; Schmidt, S. ; Mohr, H.

Springer

Planta 177 (1989), S. 74-83

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ISSN: 1432-2048

Keywords: Ammonium toxicity ; Nitrate reductase (multiple forms) ; Phytochrome ; Plastidic factor ; Sinapis (nitrate reductase)

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract In mustard (Sinapis alba L.) cotyledons, four different forms of nitrate reductase (NR) can be separated by anion-exchange chromatography. Two of these forms (NR1 and NR2) appear in the presence of NO 3 - while the other two (NR3 and NR4) appear as a response to the application of NH 4 + as the sole nitrogen source. In the presence of NH4NO3, NR3 appears to be superimposed on nitrate-induced NR1 and NR2 while the NH 4 + -induced appearance of NR4 is totally abolished in the presence of equimolar amounts of NO 3 - . The appearance of NR1, NR2 and NR3 is strongly stimulated by red light pulses which operate via the far-red-absorbing form of phytochrome (Pfr), whereas the appearance of NR4 requires continuous light (likewise operating through pytochrome). Continuous red light is more effective in this case than continuous far-red light. Analysis of the data shows that the mode of action of phytochrome (Pfr) is the same in the case of the appearances of NR1 and NR2, whereas it is quantitatively different in the case of NR3 and totally different in that of NR4. A ‘plastidic factor’ has previously been postulated to be obligatorily involved in the transcriptional control of nuclear genes encoding for proteins destined for the chloroplast. Photooxidative damage of the plastid is postulated to destroy the ability of the organelle to produce this signal. If the plastids are damaged by photooxidation, the action of nitrate and phytochrome on the appearance of NR is abolished. The plant cell regulates the appearance of nitrate-induced NR, which is cytosolic, as if it were a plastidic protein. The appearance of NR3 depends on the plastidic factor in principally the same way as that of NR1 and NR2 whereas NR4 is totally independent of the plastidic factor. The data document particular kinds of interaction between controlling factors (light, nitrate, ammonium, plastidic factor) which affect gene expression in plants. These intricacies of regulation have so far not been considered in molecular studies on NR-gene expression.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00392156

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4

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Control by phytochrome of the appearance of ribulose-1,5-bisphosphate carboxylase and the mRNA for its small subunit (1988)

Schuster, C. ; Oelmüller, R. ; Mohr, H.

Springer

Planta 174 (1988), S. 426-432

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ISSN: 1432-2048

Keywords: Gene expression (control points) ; Phytochrome, and ribulose-1,5-bisphosphate carboxylase ; Ribulose-1,5-bisphosphate carboxylase ; Sinapis

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We have measured levels of ribulose-1,5-bisphosphate carboxylase (RuBPCase) and levels of in-vitro-translatable mRNA for the small subunit (SSU) of RuBPCase up to 96 h after sowing in mustard (Sinapis alba L.) cotyledons, in order to investigate to what extent the rate of enzyme synthesis is related to the level of SSU-mRNA. Both enzyme and mRNA level are controlled strongly by phytochrome, but the rate of RuBPCase accumulation was found to be unrelated to the level of translatable SSU-mRNA. As an example, it was found that the amount of SSU-mRNA in far-red light (FR)-grown mustard seedlings doubles between 54 and 84 h after sowing while the rate of RuBPCase accumulation remains constant over this period. Since the holoenzyme shows zero turnover during this period it is concluded that the rate of enzyme synthesis remains constant although the level of SSU-mRNA increases strongly. Following an FR→dark transition, with different levels of physiologically active phytochrome (Pfr) established at the end of the light period, no correlation was found between the time course of mRNA levels in darkness and the rate of enzyme synthesis. Rather, the data indicate that there is at least one translational or post-translational regulatory step which is also phytochrome-dependent. It is concluded that coarse control of the appearance of translatable SSU-mRNA is essential for RuBPCase to appear at a high rate but that fine tuning by phytochrome of the actual appearance of RuBPCase is not transcriptional.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00959531

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5

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Signal storage in phytochrome action on nitrate-mediated induction of nitrate and nitrite reductases in mustard seedling cotyledons (1987)

Schuster, C. ; Oelmüller, R. ; Mohr, H.

Springer

Planta 171 (1987), S. 136-143

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ISSN: 1432-2048

Keywords: Nitrate reductase ; Nitrite reductase ; Phytochrome ; Signal (storage, transduction) ; Sinapis (phytochrome)

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Application of nitrate leads to an induction of nitrate reductase (NR; EC 1.6.6.1) and nitrite reductase (NIR; EC 1.7.7.1) in the cotyledons of dark-grown mustard (Sinapis alba L.) seedlings, and this induction can strongly be promoted by a far-red-light pretreatment — operating through phytochrome — prior to nitrate application. This light treatment is almost ineffective — as far as enzyme appearance is concerned — if no nitrate is given. When nitrate is applied, the stored light signal potentiates the appearance of NR and NIR in darkness, even in the absence of active phytochrome, to the same extent as continuous far-red light. This action of previously stored light signal lasts for approx. 12 h. Storage of the light signal was measured for NR and NIR. The process shows enzyme-specific differences. Storage occurs in the absence as well as in the presence of nitrate, i.e. irrespective of whether or not enzyme synthesis takes place. The kinetics of signal transduction and signal storage indicate that the formation and action of the stored signal are a bypass to the process of direct signal transduction. Signal storage is possibly a means of enabling the plant to maintain the appropriate levels of NR and NIR during the dark period of the natural light/dark cycle.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00395077

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6

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Inhibition and promotion by light of the accumulation of translatable mRNA of the light-harvesting chlorophyll a/b-binding protein of photosystem II (1987)

Oelmüller, R. ; Schuster, C.

Springer

Planta 172 (1987), S. 60-70

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ISSN: 1432-2048

Keywords: Chlorophyll (gene expression) ; Gene expression and light ; Light and gene expression ; Light-harvesting chlorophyll a/b-binding protein ; Phytochrome ; Ribulose-1.5-bisphosphate carboxylase ; Sinapis (light, mRNA)

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The amount of in-vitro translatable mRNA of the light-harvesting chlorophyll a/b-binding protein (LHCP) of photosystem II strongly increases in darkness (D) after a 5-min red-light pulse while continuous illumination of mustard seedlings with far-red (FR), red or white light leads only to a slight increase in the amount of translatable LHCP-mRNA. No increase can be observed after a long-wavelength FR (RG9-light) pulse. However, a FR pretreatment prior to the RG9-light pulse strongly increase LHCP-mRNA accumulation in subsequent D. This is not observed in the case of the mRNA for the small subunit of ribulose-1.5-bisphosphate carboxylase. The increase of LHCP-mRNA in D after a FR pretreatment can be inhibited by a reillumination of the seedlings with FR. The inhibition of LHCP-mRNA accumulation during continuous illumination with FR and the strong increase in D following a FR illumination was found to be independent of chlorophyll biosynthesis since no correlation between chlorophyll biosynthesis and translatable LHCP-mRNA levels could be detected. Even strong changes in the amount of intermediates of chlorophyll biosynthesis caused by application of levulinic acid or 5-aminolevulinic acid did not affect LHCP-mRNA levels. Therefore, we conclude that the appearance of LHCP-mRNA is inhibited during continuous illumination, even though illumination leads to a storage of a light singal which promotes accumulation of translatable LHCP-mRNA in D.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00403029

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